With development in various industrial fields, a demand for a small hydrogen production apparatus for on-site or on-board use is expected to increase. A large-scale hydrogen production process commercially available in the art is shown in FIG. 1. That is, hydrocarbons are converted into a synthetic gas including hydrogen and carbon monoxide in a reforming apparatus 10 and the synthetic gas is subjected to water gas shift (WGS) in an WGS reactor 20, followed by removal of carbon monoxide from the reformed gas through a catalyst or a separation membrane in a hydrogen separator 30, thus resulting in hydrogen. In this regard, a heat of reaction (‘reaction heat’) required in the reforming apparatus 10 may utilize a combustion heat generated from a burner 40 by burning a part of the produced hydrogen.
Production of hydrogen using hydrocarbons may be performed according to a variety of reactions such as the following reaction schemes 1 to 3:CH4+H2O→CO+3H2 reaction heat:+206 kJ/mol  Reaction scheme 1CO2+CH4→2CO+2H2 reaction heat:+247 kJ/mol  Reaction scheme 2CH4+½O2→CO+2H2 reaction heat:−36 kJ/mol  Reaction scheme 3
Among the foregoing, stream reforming according to Reaction scheme 1, wherein a reaction product has the highest hydrogen concentration, has drawn much attention in the related art.
However, the process entails difficulties in supplying heat required for reaction, as illustrated in Reaction scheme 1. Since the steam reforming may impart a conversion of hydrocarbon (methane) of 95% or more at a reaction temperature of 750° C. or higher, arduous and constant efforts are required in order to supply a reaction heat while maintaining a high temperature.
The reaction heat required for Reaction scheme 1 may be generated through combustion (catalyst oxidation or combustion), as shown in Reaction scheme 4.CH4+2O2→CO2+2H2O reaction heat:−801 kJ/mol  Reaction scheme 4
In a process according to Reaction scheme 4, in order to ensure efficient heat transfer, a high temperature difference ΔT, a great contact area ‘A’ and a substance having a high heat transfer constant ‘k’ are required.
In a process according to Reaction scheme 4, in order to ensure efficient heat transfer, a substance having a high temperature difference ΔT, a great contact area ‘A’ and a high heat transfer constant ‘k’ is required.
However, it is impossible to raise a temperature of a flame without constraint, which is needed for heating, to obtain a desired high temperature difference. Also, constitutional materials of reactor may entail restrictions, and the heat transfer constant may be determined as an inherent value of each of such constitutional materials, thus entailing limitations.
Accordingly, a heat transfer area ‘A’ is only controllable item in construction of a reactor, tends to increase.
As the reactor for the foregoing use, there have been attempts to utilize a reactor having a micro channel on a metal sheet. In particular, the applicants of the present invention suggested and developed Korean Patent Registration No. 10-0719486 (a micro-combustion/reforming device) and Korean Patent Application No. 10-2009-0124091 (a hydrocarbon reforming device using a micro channel heater), the above inventions have disclosed a micro-combustion/reforming device with a module configuration by laminating processed metal sheets in plural, so as to ensure a larger contact area per unit volume.
Combustion of hydrocarbons (NG, LPG, alcohols) for generating the reaction heat is a violent (active) reaction generating exothermic heat in large quantities and proceeds through catalytic combustion or non-catalytic combustion.
The catalytic combustion includes preheating of a catalyst layer to a reaction temperature range, at which oxidation may be initiated, and entails a problem of durability of a micro channel coated with the catalyst, when exposed to heat for a long time. That is, for an oxidative catalyst, when the catalyst is exposed to heat throughout operation of a burner, it is difficult to continue oxidative activation, thus entailing restrictions in utilization thereof. On the other hand, the non-catalytic combustion cannot be applied to a compact micro channel reactor since a space for extending ignition flame is required.
A hydrocarbon reforming catalyst is utilized in various forms and a variety of patents and related documents disclose catalyst coating methods, however, there is still a need for specific configurations of a reactor, which are compatible with characteristics of a micro channel reactor, to be applicable thereto, as described in the present invention.